The practical telephone handbook and guide to the telephonic exchange (1906)
Poole, Joseph · New York, Macmillan Co. · leaf 212
sizes of copperwire are used for the leads—viz., Nos. 20 and 22 S.W.G. Asan example we may take a branch exchange at a distanceof 500 yards from the main. For this 1 pair of No. 20wires would be sufficient for a traffic equal to a maximum of5 connecting-cord circuits in use at the same time, and 2… … S BARS _ I BATTtRVAT Public EuchamGC LT Subscribers Line. Circuit. Fig. 214 the sub-exchange lines. As lamp signals with the necessaryrelays would require more current than could be economicallyfurnished through the supply leads, it is the practice to usesome form of self-restoring annunciator,…
Telephone
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